One-piece reflective marking sheet and method of making

ABSTRACT

A continuously formed, low profiled reflective pavement marker comprising a multiple, inclined, low profiled reflective portions, which are integrally connected by horizontally, positioned reflective sheeting. Each raised reflective portion integrally having multiple reflective cube corner elements within two defined inclined reflective faces. Each of the two opposite reflective faces are integrally supported by load carrying structural walls in a multi-directional manner, said load carrying structural walks define cell like areas within each inclined reflective face. A method of making said reflective marker is disclosed that includes the steps of sealing and coloring the lower portion of the reflective marking sheet.

FIELD OF THE INVENTION

[0001] This invention relate to forming reflective pavement markingarticle with multiple, precise raised reflective faces whichmonolithically including micro cube corner reflective elements withindefined cell like areas.

BACKGROUND

[0002] Unitary raised reflective pavement marking have been extensivelyused to direct roadway traffics by retro reflecting incident lights toincoming automobiles.

[0003] This type of reflective marking usually augmented either byseveral non-reflective markers, intermittent paint strips or sheets ofpolymeric stripping.

[0004] Varieties of raised reflective marking products are readilyavailable for use directly on roadway, thereby complimenting paintstriping or other raised non-reflective markers.

[0005] Alternatively, various sheet marking have been developed as analternative composition for such long, intermittent lane marking forroadway.

[0006] Several methods of making reflective sheeting for such pavementmarking have been developed. Such previous arts include multiple raisedportions with retro-reflectivity.

[0007] As an example, U.S. Pat. No. 6,303,058 B1 to Kelley et al thatuses a top, preformed reflective sheet with pre-embossed cube cornerreflective elements.

[0008] This sheeting comprised of multiple, preformed and bondedlaminate that needs to be bend into multiple raised portions without anyintegrally formed load carrying walls, then applying a filling materialinto the cavities to provide the structural support needed and to retainthe raised reflective faces in position.

[0009] Other available arts of making reflective sheets with multiple,raised reflective regions are the type that embed optical elements, suchas preformed spherical beads, into a binder resinous layer, as in U.S.Pat. No. 6,326,053 B1 assigned to 3M innovative Property Company.Various arts of forming or embossing cube corner elements on eitherspecific length of plastic articles or on continuous sheeting areavailable; U.S. Pat. No. 3,712,706 to Stamm, which is incorporatedherein by this reference, explains in detail the method of forming suchreflective sheeting. Also referenced herein are U.S. Pat. No. 3,873,184to Heenan et al; U.S. Pat. Nos. 3,684,348, 3,689,346, 3,810,804 and4,244,683 to Rowland and U.S. Pat. No. 4,025,159.

[0010] The object of this invention is to provide a novel method ofintegrally forming a by-directional partition and load carrying walls insupport of each two opposing, raised reflective faces within areflective sheeting, thereby eliminating the need for back-filling theseprotruded cavities with resinous material for structural support.

[0011] It is further objective of this invention is to provide a methodof manufacturing reflective sheeting having multiple, raised reflectivefaces in relatively inexpensive and with uniform dimension.

[0012] The incorporation of monolithically formed load carryingstructural walls defining multiple cube corner elements within cell likeareas has been explained in detail in U.S. Pat. No. 6,334,734 andapplication Ser. No. 09/982,044 belonging to this applicant, which areincorporated herein by this reference.

SUMMARY OF INVENTION

[0013] The present invention relates to improved pavement marking havinglow profiled reflective faces with multiple of integrally formedstrippings.

[0014] The present invention also includes an efficient method offabricating the reflective pavement marker.

[0015] The reflective faces as well as the integrally connectedstripping portions incorporate multiple of micro-prismatic cube cornerreflective elements within the internal surfaces of the cell like areas.The cell like areas are defined by a multi directional or by directionalload carrying partition walls depending on the size and height of thereflective faces being incorporated.

[0016] Several methods are available for manufacturing the presentinvention.

[0017] A continuous method of production would include a compressionmolding techniques.

[0018] This method comprises of a continuously fed, opticallytransparent sheet which pass through cavity pre-forming station undersufficient vacuum or pressure to pre-form a contoured surface nearly theshape of the cavities of the compression molding die.

[0019] This top transparent continuously fed sheet can be made ofacrylic, polycarbonate or other transparent and ultra violet stableresin of good optical transparency. This transparent sheet can also bepre coated with abrasion resistance hard carbon, silicone dioxide oraluminum trioxide film, utilizing reactive sputtering or chemical vapordeposition methods.

[0020] Then a resin dispensing station would inject a transparent,resinous fill material.

[0021] The pre-calendared, filled surface then move to a compressionmolding station having a core segment that simultaneously imprint both,the cube corner reflective elements as well as the load carryingpartition walls monolithically on top of said transparent sheet thencure the composite marker.

[0022] A compatible sealing sheet would be laid at the base area of thecomposite marking article, then welding to said base region to form thefinal reflective pavement marker.

[0023] A conveyerized rotational means can continuously move the cavityportion of the compression die, thereby strip release the finishedpavement marker onto the next station of cutting and packing.

[0024] The production method may include several in between substationsuch as vibrating the fill surface to eliminate air bubbles, heat, airor cooling water supplies or trimming equipments, as needed.

[0025] The raised reflective pavement marker of the present inventionincludes several advantages over other sheet type or single reflectivepavement markers.

[0026] This type of reflective marking are suited for replacing thecombined pavement lane stripping as well as the raised reflectivemarkers used with such lane stripping. It also can be used as pavementsigns and directional markings.

[0027] Additionally, this type of retro-reflective marking can be veryeffective for pedestrian crossing, especially during intensive rain.

[0028] This type of sheeting can also find used on vertical objects suchas truck trailers, vertical posts, embankments, side curbs, delineators,etc.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention will be described in connection to the accompanieddrawings in which:

[0030]FIG. 1 is a cross section of a segment portion of a reflectivepavement-marking sheet;

[0031]FIGS. 2, 3 are isometric view of a cross section segment for areflective pavement marking.

[0032]FIG. 4 is a segment of a pavement marker used for pedestriancrossing that can be formed in accordance to the invention;

[0033]FIG. 5 is a schematic view of a preferred apparatus showing thesequence of a production method in accordance to the invention;

[0034]FIG. 6 is a magnified cross sectional segment of acompression-molding tool for forming the retro reflectivepavement-marking sheet;

[0035]FIGS. 7, 8 show a cross section and elevation views of a highprofiled, raised reflective portion in accordance to present invention;and

[0036]FIG. 9 is a magnified plane view depicting range in the hexagonalarray of cube corner retro reflectors used in accordance with presentinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0037] Referring now to FIGS. 1 and 2 of the drawings, shows afragmentary cross section view of a portion of the embodiments of thisnovel reflective pavement marking sheet, said fragment is designated asmarker 10 which comprises multiple raised reflective portions 12 eachfollowed by a planar reflective flat sheet 18. A typical reflectivesheet may contain hundreds of raised reflective portions 12intermittently connected with planar reflective sheet 18. The length ofsuch reflective sheet having multiple reflective portions 12 can besubstantially continuous to any desired length that would be applicablefor roadway usage. Each raised reflective portions 12 have an exteriorcomprising of a top surface 16, two inclined reflective faces 14 onopposite directions, two inclined or arcuate sides 29. When the desiredreflective portions 12 is having significantly higher profile of about0.2 to 0.5 inch an arcuate sides 29 can be formed intermittently, asshown in FIG. 8, and at any desired intervals within a giving width ofsaid reflective pavement marking sheet 10, otherwise for a reflectiveportion 12 with lesser heights, the sides 29 can have a simple inclinedsurfaces.

[0038] Each of the reflective faces 14 has an inside surface withmultiple of integrally formed micro cube corner reflective elements 20defined by multi directional load carrying partition walls 22.

[0039] For wider reflective portion 12, the partition walls 22 may besub divided into multiple walls, as shown in FIG. 7. FIG. 8 is a typicalelevation view of a high profiled reflective portion 12. Hollow cavities24 are integrally formed separating the apexes of the cube cornerreflective elements 20 within inside of each inclined reflective face 14and the multi directional load carrying partition walls 22 that defineeach of said face.

[0040] The reflective flat sheets 18, which integrally connect each tworaised reflective portions 12, have an exterior planar surface that mayincorporate slightly raised bumpers 27 and a lower base surface withmultiple cube corner reflective elements 20 either within cell likeareas defined by slightly raised ridges 28 or it can be without anyridges 28.

[0041] Bumpers 27 can be eliminated when the reflective flat sheets 18are short spanned.

[0042] A backing sheet 26 is welded onto the lower base surface of thereflective flat sheets 18 and the tips of the load carrying partitionwalls 22 within each raised reflective portions 12. Adhesive may be preapplied to the backing sheet 26 for adhesion to the roadway surface.Various polymeric materials may be used to form the reflectivepavement-marling sheet 10. This polymeric material can be either in acomposite form or a single polymer having a high resiliency, goodabrasion resistance and ultra violate resistance. Polymer such aspolymethyl methacrylate, polybutyle acryl ate, cellulose esters orpolycarbonate are among the preferred resins used to form pavementmarker 10.

[0043]FIG. 3 shows an isometric view of a section for anotherembodiment, a segment of a reflective pavement marker 10 b which isessentially the same as pavement marker 10 having raised reflectiveportions 12 with only one directional load carrying partition walls 22that support the reflective faces in the direction of traffic. This typeof reflective pavement marker is adequate when low-profiled reflectivefaces are preferred.

[0044]FIG. 4 shows a segment of a reflective marker sheet that can beused for pedestrian crossing or barrier marking having multiple of longraised reflective portions 12 facing the traffic direction.

[0045] Directional arrows or other signs can be cut from such reflectivesheeting with variation in cross-sections of present innovativeinvention.

[0046] When a composite material is used to form pavement marker 10, atransparent colorant can be added to the polymeric material formingeither the upper or lower portion there off. It would be essential thatthe polymeric components selected for forming reflective pavement marker10 to be compatible with each other and tenaciously here to each other.The spacing between the raised reflective portions 12 can be about 1 to48 inches, depending on the size of the raised portions 12 integrallyincorporated within reflective sheeting. Diagrammatic illustration ofthe method of a continuous production apparatus for the fabrication ofreflective pavement marking sheet of the type is illustrated in FIG. 5.The production apparatus includes a rotationally movable carriage means40 that is generally comprises of a belt structure that includesmultiple portions of the cavity side for the compression molding station53. If needed, heating, pressure, air and cooling elements can beincorporated into the cavity segments 35 within the carriage means 40. Amagnified cross sectional segment of typical elements of a compressiondie 53 is shown in FIG. 6. Referring now to the fabrication process,transparent sheet line 19 of a polymeric material is fed thru station 50onto a horizontally positioned region directly above a horizontalsegment of the rotationally movable carriage means 40. Carriage means 40sequentially moves multiple cavity portions 35 toward the compressiondie station 53.

[0047] At the pre-shaping station 51 the sheet line 19 is slowly moldedinto the cavities of the movable carriage means 40 at the horizontalsegment. This pre-shaping station may apply vacuum or just mechanicalmeans or both for pre-forming the desired exterior shape of thereflective pavement marker 10.

[0048] The sheet line 19 at station 51 would be in a slack mode, therebyallowing either the mechanical smooth core 51 a or the vacuum meanswithin station 51 to shape exterior portion of said reflective pavementmarking sheet 10. The mechanical smooth core 51 a can be designed tooperate sequentially utilizing various sliding means that can beincorporated as part of the core elements (51 a), thereby pushing thesheet 19, first by the furthest smooth faced core 51 a into thecorresponding cavity 35 within carriage 40, then the next core elementsthereof. Using thicker sheet 19 can provide an alternative means so thatsheet 19 would not splinter during the pre-compression or vacuuming intothe cavity shaped position. Heating, pressure, air and cooling meanswould be available at station 51 for use as needed. Next station 52 is apressurized resin dispensing system that can be fitted with a meteringdevice, heating timer, manifold and a mixing head for injection of anoptically transparent viscous resin. This station 52 can be fitted witha recycling shoot and an override mechanism so that if accidentalmaterial dispensing takes place, it can be over ridden manually, therebyutilizing pre mixed patches of resin. An internal release additive maybe incorporated into the transparent resinous polymer or an externalrelease agent may be applied to the compression molding dies, or both asneeded.

[0049] Station 57 is a calendaring roller or skimmer to retain anyaccess resinous material and divert it into a recycle tank. Station 57can be supported with vibration devices to eliminate air bubbles thatmay be entrapped during resin injection process.

[0050] Station 53 is the compression molding segment of thiscontinuously forming cycle, which is fitted with the core heads 30,either in a singular core head or multiple core heads as shown in FIG.5.

[0051] A magnified cross section segment of one of the core heads 30 isshown in FIG. 6 together with a segment cross section of a reflectivepavement marker 10.

[0052] Also shown in FIG. 6 is a cross section segment of thecorresponding cavities 35 that would be attached to the rotationalcarriage means 40.

[0053] Station 53 is provided with pressure, heating, cooling, air andwater lines to be used as needed. Core head 30 has multiple microprismatic cube corner reflective element pins together with the cavitiesfor forming the multi directional load carrying partition walls 22.Several methods can be used to fabricate core head 30. One of thepreferred methods is to electroform the entire upper part to a thicknessof about 0.3 to 0.5 inch or more if needed from metal alloys such asnickel cadium then a backing or thickening metal will be applied tostrengthen the first, upper detailed segment. All cavity moldings forthe load carrying partition walls 22 as well as the hexagonal micro cubecorner reflective elements 20 would be within this core segment 30.

[0054] Proper draft slopes would be incorporated within the wall limitsof this core molding to allow uninterrupted release after compressioncycle time.

[0055] After the compression molded segment 10 is cured, an additionaltime station or space may be required for cooling interval of thecomposite sheet formed by bonding of the transparent sheet surface 19 tothe cured resinous material defining the cube corner elements 20 and thewall elements 22.

[0056] A release agent may be incorporated into the resinous material orexternally applied to the core and cavity to allow proper separation ofthe finished sheet.

[0057] Next station 54 is for applying the backup protective sheet 26,which is a thin and compatible plastic, to the base portion of thereflective pavement marker 10.

[0058] The backup sheet 26 can be either agglutinated or welded ontoeither a designated, raised wedge like walls 28, forming rectangulargrid like cells within the lower surface of planar reflective sheet 18,or can be directly welded onto the apexes of the multiple cube cornerreflective elements 20 within said lower surfaces of planar reflectivesheets 18 and the tips of the wedge shaped ends of the load carryingwalls 22.

[0059] When abrasion resistance surface is needed the continuouslyrolled transparent sheet 19 can be pre-coated continuously with aluminumtrioxide, hard carbon or silicone dioxide utilizing one of variouschemical vapor deposition methods or reactive sputtering method. Thesubstantially continuous transparent sheet 19 can also be made with anydesired transparent coloration. The reflective pavement marker sheet canalso have only the lower, prismatic cube corner reflective elementsimpregnated with transparent colorant prior to compression molding thereflective pavement-marking sheet. Both the transparent sheet 19 and theresinous polymer have to be highly stable against ultra violate light.

[0060] Station 55 is for pre application of adhesive to the base surfaceprior to reaching the cutting and storage station 56.

[0061] Various thickness of the transparent sheet 19 can be used in thisprocess depending on the size of the protruding reflective portions 12.Commonly used thickness for sheet 19 is about 0.002 to 0.05 inch.

[0062] Once the combined composite reflective pavement marking sheet toadvance from station 55 to the cutting and storage station 56, therotational direction of the cavity portions 35 within station 40 willallow the release of the finished product toward the cutting region.Stations 50 thru 55 can be synchronized to functions eithersimultaneously or sequentially with an override control within everystation.

[0063] It is clearly understood that this method is applicable tomanufacturing one-piece single reflective pavement markers as in U.S.Pat. No. 6,334,734, application Ser. Nos. 09/634,430, 09/880,780 and09/982,044 to Attar with minor adjustment and cutting retrofits.Alternative methods of continuous production of this novel invention canbe achieved. An example of such alternative would include modifiedstations within a method such as in the previous art of U.S. Pat. No.3,689,346 to Rowland. This is especially feasible when the desiredreflective marking 10 require very low profile, having a reflectiveportions 12 with a height equal or less than 0.20 inch. While the cavityportion of such embossment can be incorporated as a belt around a drumof various sizes or forms, then a transparent flexible film 19 isapplied to the cavity belt A corresponding pressure drum with the coreelements fixed on a belt, mounted onto said drum. This core belt drummust have synchronized reverse motion with respect to the cavity drum.

[0064] A designated spacing is to be allowed between the two reversemoving drums, thereby filling the cavities within the embossment moldingcreated between the two drum faces, whereby embossment of the cubecorner reflective elements 20 as well as the load carrying partitionwalls 22 will takes place.

[0065] In order to complete this process cycle, an additional stationmust be added to allow the adhesion of a backing, protective-sheeting 26onto the lower portion of the continuously formed reflective sheeting 10to complete such production process.

[0066] It is understood that various changes or modifications can bemade within the scope of the appended claims for the above-preferredmethods for forming the present reflective pavement-marking articlewithout departing from the scope and the spirit of the invention. Theprinciple processes of this invention are not limited to the particularembodiments described herein. Various embodiments can employ theprocesses of this invention. This invention is not limited to the exactmethods illustrated and described; alternative methods can be used toform the intended reflective pavement marker of this invention.Therefore, the invention can be practiced otherwise than as specificallydescribed herein.

What is claimed is:
 1. A one-piece retro reflective pavement markingsheet comprising: integrally formed upper reflective surface and lowerprotective sealant sheet, said upper reflective surface having multiple,inclined reflective portions, each followed by a planar horizontallypositioned reflective sheet, said inclined reflective portions eachhaving an arcuate top, inclined or arcuate sides and two oppositelypositioned inclined planar reflective faces, said planar reflectivefaces each having a planar outside and inside surfaces, said insidesurfaces of planar reflective faces each having multiple, integrallyformed micro cube-corner reflective elements; load carrying partitionwall means for providing structural support and defining substantiallyhollowed inside surfaces of said raised reflective portions, said planarhorizontally positioned reflective sheet each having an outside planarsurface and an inside surface integrally formed with multiple micro cubecorner reflective elements, said load carrying partition wallsintegrally provide the structural support needed.
 2. The one-piece retroreflective pavement marking sheet as defined in claim 1, wherein thereflective faces of said reflective portions and the planar,horizontally positioned reflective sheets can be formed having exteriorsurfaces with cell-like regions defined by slightly raised ridges toeliminate tire contact.
 3. The one-piece retro reflective pavementmarking sheet as defined in claim 1, wherein the entire base region ofsaid upper reflective surface is backed with a flexible, protectivesealant sheet, said sealant sheet is being welded onto the wedged endsof said load carrying partition walls and the apexes of said multiplecube corner reflective elements within each horizontally positionedreflective sheet areas.
 4. The one-piece reflective pavement markersheet as claimed in claim 1, wherein the raised reflective portions areof about 0.05 to 0.50 inch in height and of about 0.5 to 12 inches inwidth.
 5. The one-piece reflective pavement marking sheet as claimed inclaim 1, wherein each horizontally positioned reflective sheetlongitudinally connecting each two rows of said raised reflectiveportions is about 0.50 to 36 inches in length, said horizontallypositioned reflective sheets can have grid like raised wedges of about0.005 to 0.05 inches to eliminate direct tire contact, said horizontallypositioned reflective sheets having inside surfaces with multiple microcube corner reflective elements.
 6. A method of forming a reflectivepavement marker in the form of a continuous sheet of transparentpolymeric material having a top reflective sheet and a backup sealersheet for adhering to the pavement, said top reflective sheet dividedinto multiple raised reflective portions intermittently connected withplanar horizontal reflective sheets, said raised reflective portionseach having an exterior surface and a substantially hollowed interiorsurface, each exterior surface comprising of an are top, two inclinedsides and two planar inclined reflective faces, said reflective portionseach having an interior surface integrally formed with multiple microcube corner reflective elements within designated inside surfaces ofsaid inclined reflective faces defined by multiple load carryingpartition walls, said planer horizontal sheets each having insidesurface integrally formed with multiple cube corner reflective elementsseated with said backup sealer sheet, the steps comprising: a.continuously passing a sheet of flexible transparent polymeric thin filmof substantially continuous length over a horizontally positioned regiondirectly above a rotationally moving cavity carriage means under slowand sequentially applied pressure and or vacuum allowing the flexiblefilm surface preliminarily to contact and take shapes of the innercontours of the compression molding cavities, said movable cavitycarnage means generally comprises of a sequentially moving beltstructure that includes multiple cavity portions of a compressionmolding apparatus; b. injecting a curable, optically transparentresinous material on top of said cavity segments of said rotationallymoving cavity age means containing the preformed flexible thin filmwithin the horizontally positioned region, thereby filling thepre-shaped cavities within the flexible film sheeting with a sufficient,quantitatively scaled curable transparent resinous material andcontinuously skimming any access of said material thereof prior tomoving to the next step; c. passing said preformed thin film sheetingtogether with the transparent resinous material under the compressionmolding station utilizing pressure as well as heating to thesynchronized compression die core segment that correspond to each movingcavity segment within the rotationally moving cavity carriage means,whereby applying sufficient pressure and heating to bond and solidifythe continuously moving composite segments of said reflective pavementmarking sheet with the integrally formed cube corner reflective elementstogether with the solidified load carrying partition wall means; d.passing said solidified continuously formed composite reflectivesheeting under a calendar roller which firmly apply the backup sealersheeting to the solidified base surface of said continuously formedcomposite reflective pavement marking sheet prior to passing under thebonding station where the backup sealer sheet is welded onto the baseportion of said continuously formed composite reflective sheeting; ande. applying one component adhesive to said backup sealer sheet as wellas applying a removable protective covering for said adhesive as needed.7. The method set forth in claim 1, including the sequentially insertingand pre-forming means for allowing the transparent flexible sheetingsegment to take the contour shapes of the cavities within a segment ofsaid rotationally moving cavity carriage means, said pre-forming meansmay be provided with pressure, heating as well as vacuum, saidpre-forming means is synchronized with all of the forward movingsegments of said continuously forming process of said reflectivepavement marking sheet.
 8. The method set forth in claim 1, wherein thesubstantially continuous flexible sheeting can be pre-coated with a hardcarbon, aluminum oxide or silicon dioxide film utilizing reactivesputtering or one of various chemical vapor deposition methods in acontinuous means.
 9. The method set forth in claim 1, wherein thecompression molding apparatus may be provided with pressure, heating andcooling means, said compression molding apparatus would be synchronizedin motions with all previous sub-stations.
 10. The method set forth inclaim 1, wherein the transparent polymeric resinous material can beselected from one of various groups of plastic materials such as acrylicester resins, hydrocarbon resins or polycarbonates, said polymericresinous material must be tenaciously compatible with said pre-formedflexible transparent sheeting.